top speed only 15 mph on 86 bayliner cierra aq125 volvo penta 270

[rolandas]

top speed only 15 mph on 86 bayliner cierra aq125 volvo penta 270,any suggestions?switch about ten different props,no luck,reverse very slow also

 

[Don S]

Re: top speed only 15 mph on 86 bayliner cierra aq125 volvo penta 270

What is your WOT (Wide Open Throttle) rpm?

 

[rolandas]

Re: top speed only 15 mph on 86 bayliner cierra aq125 volvo penta 270

4400 rpms

 

[jerryjerry05]

Re: top speed only 15 mph on 86 bayliner cierra aq125 volvo penta 270

If it is the original drive.Is it the VOLVO prop?Not an aftermarket.
Is the speed reading from the boat speedo? If so the pitot tube could be clogged.Or not reading right. Can you get a GPS to test your speed.Jerry

 

[Don S]

Re: top speed only 15 mph on 86 bayliner cierra aq125 volvo penta 270

You are about 400 rpm low, but you aren't going to gain 15 or 20 MPH by getting that 400 rpm back.
However, the boat may be trimmed wrong and propped wrong for that trim, or it may be just a slower hull design. There were some semi displacent hulls in the early 80's bays that only went 15 to 20.

 

[Robj]

Re: top speed only 15 mph on 86 bayliner cierra aq125 volvo penta 270

So your WOT rpm is 4400 and you are only doing 15 mph? And you have tried different props? So that means that it is not a prop slipping problem, because with all the props you tried, it is extremely unlikely that all are slipping. How did you measure the speed? Did you verify it with GPS? Need a little more info.

Have a great day,

Rob.

 

[rolandas]

Re: top speed only 15 mph on 86 bayliner cierra aq125 volvo penta 270

i have two speed meters(brand new) both shows the same,and i feel i going slow ,both was bought 3 monts ago,previous owner told me rebuilt outdrive its on,props what i have changed is good,even from similar boats with 35-40 top speed,the boat was going revers very slow also...please help, have no idea where to start,maybe lower-uper units mixed,clutch?,etc,engine 4 cylinders,boat 21 foot long,checkd by certified mech everything ok,changing of props just get me down to 12-10 even 7 mph,restore that boat from the bottom,put a lot of money,it must go at least 25-30 mph???
thank you

 

[jerryjerry05]

Re: top speed only 15 mph on 86 bayliner cierra aq125 volvo penta 270

That boat should do 30.If they replaced the drive instead of rebuilding it's possible he used a drive from a different gear ratio.
A friend had a 23 ft with the same motor and wasn't happy with the way it ran.So he did a tune up and oil change then he put a Michigan prop on it.
I didn't work on the boat till after he started having performance problems.
He looked me up.
He explained the tune up not the prop change.
I started looking and couldn't find anything wrong.
Then I saw the original VOLVO prop on the ground and asked him if it was a good spare.Then he said no it was the original.I told him to put it back on and go for a ride,It was the problem.
Some of those units just don't perform with anything other than original.
On the upper drive is a plate with the ratio.Check it out.Jerry

 

[chiefalen]

Re: top speed only 15 mph on 86 bayliner cierra aq125 volvo penta 270

Hows the foam in the hull wet?

 

[rolandas]

Re: top speed only 15 mph on 86 bayliner cierra aq125 volvo penta 270

thanks but i still have the problem.

 

[jerryjerry05]

Re: top speed only 15 mph on 86 bayliner cierra aq125 volvo penta 270

Find the person who rebuilt the drive or replaced the drive.Did you check the ratio? If you changed the props and no change then the drive is your problem.

 

[bamadave]

Re: top speed only 15 mph on 86 bayliner cierra aq125 volvo penta 270

Does the boat stay in the water? If so, maybe dirty bottom?

 

[rolandas]

Re: top speed only 15 mph on 86 bayliner cierra aq125 volvo penta 270

bottom clear,and i can t see this ratio numbers on plate.but if i change the lover unit ? thank you for your help.